Additives to Improve Efficiency of Animal Production - Part I
The next two sections will discuss various feed additives added to rations
to improve the efficiency of animal production via an improvement in intake,
digestion, and/or metabolism efficiency, and/or health of the animal.
Adequate feed intake is essential to meet the daily nutrient requirements
of an animal and for efficient animal production. Flavoring agents are
feed additives added to the ration to improve palatability and acceptance
of a feed and to facilitate feed intake. Feed additives are especially
beneficial for animals consuming rations with low palatabilities, animals
in distress, and high-producing animals.
Smell and taste are important senses in feed flavor and acceptance. The
four primary taste sensations are sweet, bitter, salty, and sour. The
sensory abilities and preferences vary by species. In general, herbivorous
and omnivorous animals prefer sweet compounds. Select species have also
displayed preferences for specific volatile fatty acids. Horses possess
acute senses of smell and taste. Poultry possess a minimal sense of smell
and an adequate sense of taste. Ruminants possess a sense of smell and
taste.
Flavoring agents may be classified as natural flavors, nature-identical
flavors, or artificial flavors. Natural flavors are substances obtained
via physical methods from raw materials. Nature-identical flavors are
substances chemically identical to natural products and are obtained via
chemical methods from raw materials or chemical synthesis. Artificial
flavors are produced via chemical synthesis and are not present in natural
products. In comparison to natural products, synthetic products may be
superior to natural products regarding consistency of quality, ability
to endure processing methods, and cost-effectiveness. Regardless of the
origin, a specific flavor is frequently the result of a complex mixture
of chemicals. Numerous flavoring agents are present in natural feedstuffs
and available as additives to improve the flavor and acceptance of feedstuffs.
Enzymes are organic catalysts. Enzymes are complex protein compounds produced
by the cells of plants and organisms. In general, enzymes produced by
the animal are adequate for the digestion of proteins, lipids, and carbohydrates
specific to the enzymes produced. However, animals do not produce enzymes
for the digestion of each component of the ration. Therefore, additional
enzymes fed as additives in the ration have the potential to digest nutrients
not digested by the enzymes produced by the animal or the microorganisms
within the animal.
For nonruminants, enzymes to digest cellulose have not been effective
or economical. Enzymes added to rations of monogastrics are beta-glucanase
and pectosanase. Beta-glucans are structural carbohydrates present in
feeds such as barley and oats. Beta-glucanases added to the rations of
poultry fed barley or oats have improved the growth rate, feed efficiency,
and properties of the excrement of the animals. Beta-glucanases are obtained
from fermentation products. Pectosans are structural carbohydrates present
in feeds such as wheat, triticale, and rye. Pectosanases added to poultry
rations containing wheat, triticale, and rye improved animal performance
and properties of animal excrement. For ruminants, data support cellulases
have improved digestion of structural carbohydrates in the rumen.
Buffers are compounds added to reduce the change in hydrogen ion concentration
produced with the addition of acids or alkalis. Hydrogen ion concentration
is expressed as pH. The pH is a measure of the acidity or alkalinity of
a solution. The pH of a solution is expressed on a scale of 0-14; acids
are less than 7, neutral is 7, and alkalis are greater than 7. Buffers
are added to the ration of ruminants. In general, the optimal pH of the
rumen is 6.2-6.8. Maintenance of rumen pH is essential for rumen function
and animal productivity. An excessively acidic pH alters the population
of microorganisms subsequently influencing the efficiency of digestion
of nutrients. An acidic pH also may be detrimental to the health of the
animal.
In modern production systems of ruminants, various factors contribute
to an acidic pH. The relatively low roughage content contributes to an
acidic pH. In ruminants, roughages stimulate production of saliva. Saliva
contains natural rumen buffers. Particle size of the roughage is also
important to stimulate adequate saliva production. Another factor is the
relatively high concentrate content in the ration. Concentrates are associated
with an increase in carbohydrate degradation and an increased rate of
carbohydrate degradation which results in alterations of the proportions
of volatile fatty acids in the rumen. Reduced particle size of the feedstuffs
in the ration, rapid transitions from high roughage rations to high concentrate
rations, and feeding of fermented feedstuffs may also reduce the pH of
the rumen.
Various buffer products are available. Common compounds utilized as buffers
are sodium bicarbonate and magnesium oxide. Additional compounds utilized
as buffers include potassium bicarbonate, sodium bentonites, sodium sesquicarbonate,
and limestone. Sodium bicarbonate is the primary natural buffer in a ruminant
animal.
In general, buffers may be added to the rations of dairy cattle, feedlot
beef cattle, and feedlot lambs. For lactating dairy cattle, buffers can
decrease rumen acidity and improve intake, milk-fat, and milk production.
For feedlot animals on high-concentrate rations, buffers can counteract
the depressed appetite, reduced feed efficiency, and reduced gains associated
with increased acidity in the rumen. Optimal product to add to a ration
varies by animal species, feedstuffs present in the ration, and economics.
Grit sources may be added to poultry rations to facilitate the digestion
of feedstuffs. For poultry, feed is ground in the gizzard, reducing the
particle size and facilitating subsequent digestion of feeds. Grit is
retained in the gizzard and aids in the grinding of feeds in the gizzard.
In general, grit is most effective for hard feeds and feeds with larger
particle size. Limestone and oyster shells are grits fed to poultry. In
addition, as these sources grind apart in the gizzard, they provide poultry
a source of calcium. Small stones may also be fed as grit sources.
Electrolytes are compounds when dissolved in water conduct an electric
current. In the animal body, common electrolytes are salts of the macrominerals
(i.e. sodium, potassium, magnesium, calcium, phosphorus, sulfur, and chlorine).
The most frequently administered electrolyte solution contains sodium
chloride. Additional electrolytes are solutions with potassium or magnesium
salts. In addition to daily provision in the ration, additional electrolytes
are provided in specific situations in which an animal has lost excessive
amounts of electrolytes and water. Additional electrolytes may be administered
to counteract losses resulting from diarrhea, excess sweating, excess
urination, and vomiting.
Zeolites are the primary ion-exchange compounds added to animal rations.
Zeolites are clay minerals of hydrated aluminosilicates of cations. Zeolites
are able to gain and lose water and exchange respective cations. In addition
to natural zeolites, synthetic zeolites are also available. Ion-exchange
compounds may improve growth, feed efficiency, and health of the gastrointestinal
tract of various species. Data does not support zeolites improve utilization
efficiency of NPN compounds in ruminants. Zeolites, as a feed additive
for poultry and swine, will bind ammonia and may reduce ammonia concentration
in the air in housing facilities.
Acidifying agents or acidifiers may be added to the rations of young animals.
Acidifying agents may also be referred to as organic acids. The primary
acidifiers tested are citric acid and fumaric acid. Data support addition
of acidifiers to the rations of weanling swine improved growth and feed
efficiency. Data also support addition of acidifiers to the ration of
broiler chicks improved growth rate. The mechanism of action is not proven.
Hypotheses suggest the results may be due to the antimicrobial or energy-yielding
properties of the organic acids. Acidifiers may also be included in milk
replacers for calves. Acidified milk replacers aid to maintain the abomasal
pH below a pH in which E. coli can survive.
Bloat control products function to control pasture and/or feedlot bloat
in ruminants. Bloat is a nutritional disorder characterized by the accumulation
of gases in the reticulorumen. The primary types of bloat are free-gas
and frothy bloat. Ruminants fed high-concentrate, low-roughage rations
may develop free-gas and frothy bloat. Frothy bloat may occur in ruminants
consuming immature legume forages or wheat forages. Feed additives approved
by the FDA to control bloat are poloxalene (trade name, Bloat Guard),
oxytetracycline (trade names, Terramycin and Neo-Terramycin), laureth-23
(trade name, Enproal Bloat Blox). In addition, ionophores including lasalocid
(trade name, Bovatec) and monensin (trade name, Rumensin) may be added
to high-concentrate, low-roughage rations to control bloat in ruminants.
Salivation inducers stimulate the production and secretion of saliva in
ruminants. Salivation inducers are feed additives with potential to improve
the efficiency of animal production. For ruminants, high-concentrate,
low-roughage rations are associated with inadequate saliva production
and subsequent metabolic disorders and less than optimal utilization of
feedstuffs. Interest focuses on slaframine, a fungal mycotoxin. Data from
initial studies support slaframine increases the salivation rate, rumen
pH, and efficiency of microbial protein synthesis in the rumen.
Defaunation is the process of elimination of protozoa from the rumen.
Copper sulfate, nonionic and anionic detergents, and saponins are defaunating
agents. Saponins are compounds present in plants (e.g. yucca and tropical
trees). Saponins bind cholesterol in the cell membranes of protozoa and
cause the death of the microorganism. Evidence suggests defaunation improves
the performance of ruminants fed high-concentrate, low-protein rations.
Defaunation has no appreciable effects for animals fed conventional rations.
In research, defaunation has also been utilized to study the protozoa
in the rumen.
Activated carbon may be fed to minimize the effects of specific detrimental
compounds in the gastrointestinal tract of the animal. Activated carbon
is also referred to as charcoal. Activated carbon may facilitate the excretion
of specific compounds from the gastrointestinal tract. Efficacy varies.
Activated carbon has been fed in events of pesticide and insecticide contamination
of feedstuffs.
Additives may be added to the ration to control specific aspects of the
environment. Additives to improve the interior environment may be especially
important for confined animal operations. The primary effect of the various
products is to control the ammonia in the environment. Ammonia is a gas
produced via microbial action on the urea or uric acid excreted by mammals
or birds, respectively. Excess ammonia in the environment causes respiratory
issues and a subsequent decrease in production. Added to the ration, zeolites
may reduce ammonia production in the environment. In general, application
of zeolites and other chemical compounds directly to the excrement is
a more effective method to control ammonia in the environment.
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